/Engine/Source/Runtime/Datasmith/CADKernel/Public/CADKernel/Core/Database.h
During the load of anFArchive: All Entities are saved in the session map (like Entity created in runtime) that allows to retrieve them according to their Id. Archive's entities are also saved in a temporary map for the load purpose (c.f.FEntity::Serialize) This process is automatically done during the entity creation (FEntity::MakeShared)
void AddEntityFromArchive ( [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [FEntity](API\Runtime\CADKernel\CADKernel\Core\FEntity) > Entity )